This invention relates to an apparatus and a method for forming an annular member by the use of an extruder.
In general, in order to form pneumatic tire members, such as side treads and bead fillers, annular members are often used, which are made of annular rubbers having heights in their radial direction relatively larger than thicknesses in their axial directions. Such annular members have been formed in the following manner as disclosed, for example, Japanese Patent Application Laid-open No. 1-314,151. A rubber is extruded by an extruder to form belt-shaped rubbers which are then transferred to a conical-trapezoid mold by turning transferred directions with the aid of a plurality of rollers. The belt-shaped rubbers are then attached to the outer conical circumferential surface of the mold by means of attaching rollers.
In such a hitherto used apparatus or method for forming annular members, however, the belt-shaped rubbers are cooled without being restrained therearound after they are extruded from the extruder. Therefore, amounts of elongation or contraction of the rubbers are locally different which make it very difficult to obtain a desired contour (cross-sectional shape) of the rubbers. According to the prior art, moreover, the cooled belt-shaped rubbers are attached to the mold to obtain an annular member having a larger height in the radial direction relative to its thickness. Such an annular member has the outer circumference much larger than the inner circumference. Therefore, when both ends of the belt-shaped rubbers are joined to obtain an endless annular member, the belt-shaped rubbers are locally deformed from attached positions due to internal stresses therein so that the shape of the belt-shaped rubbers are changed in various manner. Moreover, the plural rollers are needed for turning the transferred directions and attaching the rubbers to the mold, which make the apparatus complicated in construction and expensive.